Antares lofts ORB-2 Cygnus on a path to the ISS

July 13, 2014 by William Graham

Orbital Sciences launched an Antares rocket with their third Cygnus spacecraft Sunday afternoon, beginning a commercial resupply mission to the International Space Station. The rocket launched at the end of a very smooth countdown at 12:52 local time (16:52 UTC) from Pad 0A at the Mid-Atlantic Regional Spaceport.

Building upon technology developed for Orbital’s Star series of geosynchronous communications satellites, the Cygnus incorporates a Pressurized Cargo Module (PCM) developed by Thales Alenia Space and based upon the design of Multi-Purpose Logistics Modules (MPLMs) carried by the Space Shuttle.

A Cygnus variant with an unpressurised cargo section, based on another Shuttle payload – the ExPRESS Logistics Carrier – was also proposed, but this was not developed.

The Cygnus spacecraft is powered by an IHI Aerospace Delta-V engine, a derivative of the BT-4 engine, which is typically used by communications satellites.

The engine can operate in monopropellant or bipropellant modes utilising hydrazine fuel. In bipropellant mode, mixed oxides of nitrogen (MON-3) are used to oxidise the propellant.

The main engine produces 445 newtons (100 pounds) of thrust, while thirty two smaller reaction control thrusters, used for manoeuvring and orientation, each provide 27 newtons (6 pounds) of thrust.

The Pressurized Cargo Module can accommodate 2,000 kilograms (4,410 lb) of cargo and has a volume of 18.2 cubic metres (643 cubic feet). Power is provided by a pair of triple-junction gallium arsenide solar arrays which generate 3.5 kilowatts.

The forward end of the spacecraft is equipped with a Common Berthing Mechanism (CBM) which allows attachment to the International Space Station upon arrival.

Sunday’s mission, CRS Orb-2, has also been named the SS Janice E. Voss, after the NASA astronaut who died of cancer in 2012, following Orbital’s tradition of naming its Cygnus craft after astronauts.

The spacecraft is carrying 1,494 kilograms (3,293 lb) of cargo, which NASA have divided into five categories. The largest, crew supplies, consists of food and other provisions as well as clothes or hygiene equipment for the astronauts.

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The mass of this type of cargo being carried is 764 kilograms (1,684 lb). The payload also includes 355 kilograms (783 lb) of station hardware, including parts for the life support system, medical equipment, electrical and thermal control parts amongst others.

Around 8 kilograms of computer and photography equipment, and 39 kg (87 lb) of EVA hardware are also aboard.

The remainder of the cargo consists of scientific equipment and a cluster of CubeSats to be deployed from the Kibo module later this year. The other experiments include an experiment called Dynamic Surf for the Japanese Space Exploration Agency, which is aimed at studying Marangoni convection, a heat transfer process between liquids and gasses.

NASA are flying fifteen Student Spaceflight Experiment Program (SSEP) investigations aboard the mission, which will make use of resources aboard the space station to conduct research as part of an outreach program.

The TechEdSat-4 CubeSat, which will be deployed from Kibo, is one of twenty nine small satellites being carried for deployment from the station.

The satellite’s mission is to demonstrate the use of a passive deorbiting system; deploying a sail behind the satellite to increase drag. It follows the three-unit form factor, with dimensions of 10 by 10 by 30 centimetres (4 x 4 x 12 in).

The other twenty eight satellites are all part of Planet Labs’ Flock constellation.

This Antares will flew in the 120 configuration, which made its last flight. Consisting of the standard, AJ26-62 powered, first stage with an ATK Castor-30B second stage, the Antares carried its payload into Low Earth orbit.

This change will enable an enhanced version of the Cygnus spacecraft to begin flying next year.

The first stage has two AJ26 engines, which are derivatives of the Soviet NK-33 which was developed for the N1 rocket in the late 1960s or early 1970s. The NK-33 is also used as the first stage engine of Russia’s Soyuz-2-1v.

The stage structure itself was developed by Ukraine’s Yuzhnoye Design Bureau, and is based on the first stage of the Zenit rocket.

Continuing to leverage existing hardware, the second stage of the Antares, the Castor-30, was developed from the Castor-120 used as the first stage of the Taurus (since renamed Minotaur-C) rocket.

This stage, which has also been used on Lockheed Martin’s Athena rocket, was itself a new-build version of the Peacekeeper missile’s first stage, to allow Peacekeeper-derived rockets to be used for commercial missions.

Antares launches take place from Pad 0A at the Mid-Atlantic Regional Spaceport on Wallops Island.

The CRS-2 mission marked the fifth launch from the pad, which was first used in 1995 for the launch of an experimental satellite called METEOR atop a Conestoga 1620 rocket which failed to achieve orbit.

After failing on its maiden flight, the Conestoga was abandoned and Pad 0A fell into disuse. The original tower was demolished in 2008 to make way for the clean pad approach used by Orbital for the Antares, which first flew from the complex in April 2013. The three Antares launches from the pad prior to Sunday’s have all been successful.

The team that conducted Sunday’s launch were called to stations three hours and fifty minutes ahead of the planned liftoff. About three quarters of an hour later they conducted a poll for chilldown of the oxidiser lines which began ahead of oxidiser loading.

Propellant loading began following another poll at the ninety minute mark in the count.

Fifteen minutes before liftoff, Cygnus was placed on internal power, with the Antares going on internal five minutes before it launched. The automated terminal count began at the three minutes before liftoff with the propellant tanks pressurising at around the 120-second mark.

When the count reached zero, the first stage engines ignited and began to build up thrust. After 2.1 seconds the rocket was released to begin her ascent towards orbit.

Following liftoff the rocket climbed away from Wallops Island, passing through the area of maximum dynamic pressure around ninety seconds into the mission.

The first stage depleted its fuel supply around three minutes and fifty five seconds after launch, with the vehicle entering a coast phase while it ascended to an altitude of 202 kilometres (125 statute miles, 109 nautical miles).

Stage separation took place six seconds after cutoff, with the fairing separating 90 seconds later and the interstage five seconds after that. Four seconds after interstage separation the 105-second coast ended with second stage ignition.

The solid-fuelled second stage is only capable of making one burn and cannot be shut down once started, so it burned to depletion.

This took 137 seconds, providing the final impulse needed to put Cygnus into orbit.

The planned parameters for spacecraft separation, which occurred two minutes after second stage burnout, were a perigee of 197 kilometres (122 miles, 106 nautical miles), an apogee of 303 kilometres (188 mi, 163 nmi), and 51.64 degrees inclination. It is understood they were well within the parameters following ascent.

Following separation the spacecraft began its on-orbit checkout and deployed its solar arrays, before beginning a series of burns to reach the space station.

Arrival at the ISS is expected on the fourth day of the mission, with hatch opening the day after.

Cygnus is expected to remain at the Space Station for around thirty two days, during which time its cargo will be replaced with items for disposal. During its time at the station the spacecraft will be berthed at the nadir port of the Harmony module.

Following unberthing, which will also be conducted using Canadarm2, the spacecraft will perform a series of flight tests for future missions before it is deorbited to a destructive reentry a few days later.

Sunday’s was the fortieth orbital launch attempt of 2014, the eleventh of the year for the United States, and the second for Orbital Sciences.

Orbital’s next launch is scheduled for October, and will be the next Cygnus mission, CRS Orb-3. That mission, which will mark the maiden flight of the Antares 130 and the last Cygnus mission before the introduction of an enhanced cargo module, is expected to be Orbital’s only remaining launch this year.